1. Field of the Invention
The present invention relates to a vehicle having a ceramic radome, and, more particularly, to the attachment of the ceramic radome to the vehicle.
2. Description of Related Art
Outwardly-looking radar, infrared, and/or visible-light sensors built into vehicles such as aircraft or missiles are usually protected by a covering termed a radome. The radome serves as a window that- transmits the radiation sensed by the sensor. It also acts as a structural element that protects the sensor and carries aerodynamic loadings. In many cases, the radome protects a forward-looking sensor, so that the radome must bear large aerostructural loadings.
Where the vehicle moves relatively slowly, as in the case of helicopters, subsonic aircraft, and ground vehicles, some radomes are made of nonmetallic organic materials which have good energy transmission and low signal distortion, and can support small-to-moderate structural loadings at low-to-intermediate temperatures. For those vehicles that fly much faster, such as hypersonic aircraft or missiles flying in the Mach 3-20 range, nonmetallic organic materials are inadequate for use in radomes because aerodynamic friction heats the radome above the maximum operating temperature of the organic material.
In such cases, the radome is made of a ceramic material that has good elevated temperature strength and good energy transmission characteristics. However, existing ceramics have the shortcoming that they are relatively brittle and easily fractured. The likelihood of fracture is increased by small surface defects in the ceramic and externally-imposed stresses and strains. The ceramic radome is hermeticlly attached to the body of the missile, which is typically made of a metal with high-temperature strength, such as a titanium alloy.
The ceramic has a relatively low coefficient of thermal expansion (CTE), and the metal missile body has a relatively high CTE. When the missile body and radome are heated, the resulting CTE-mismatch strain between the radome and the missile body can greatly increase the propensity of the radome to fracture in a brittle manner, leading to failure of the sensor and failure of the missile. Such heating can occur during the joining operation, when the missile is carried on board a launch aircraft, or during service.
Thus, there is a need for an approach to the utilization of ceramic radomes in vehicles, particularly high-speed missiles, wherein the tendency to brittle fracture and radome failure is reduced. The present invention fulfills this need, and further provides related advantages.